745 backdoor lock lubrication?

On my 740 station wagon the back door lock cannot me operated with the key
because of too much friction apparently between the plastic cylinder and
hole in which it rotates. Maybe some MoS2-spray liquid hit it when I tried
to dissolve a sticking screw at the backdoor wiper system. The central
locking/unlocking works so that is the way I lock and unlock the backdoor
now. The problem was worse during winter in earlier years I recall but now
it has become permanent also during the dry and warm season. I have treid to
lubricate with a teflon based spray from outside whithout effect. Does
anybody have a solution for the problem besides changing the whole lock?

Viktor Weisshäupl, Vienna, Austria

 

I had the same problem with my 240 Wagon, and the problem may not be in the
cylinder as you think, but in the sliding mechanism that the cylinder
operates. You would have to remove the inside panel to gain access to it,
then remove the screws that hold the latching mechanism in place, disengage
the link rod and take the whole locking assembly out. The cylinder remains
in place. Then sand any rust off, grease the heck out of it, re-install and
enjoy. The whole process took less than 1 hour. Good Luck

Arnold

 

Thanks for the input. What I wonder is, - where does the electric mechanism
fit in. Is it working on the last members of that chain distant from the
lock cylinder?

Viktor

 

Hi Viktor, when you take this thing apart you will see that the "cam" that
rotates when you move the key, also has a rod connected to it, the rod is
operated by the lock/unlock solenoid (or motor), so that you operate the
locking mechanism either by the central locking or by the key. In any
event, if I recall correctly, there was a piston that goes through a hole,
and the whole thing was rusted shut, after some wire brush and grease, the
whole thing was as good as new. The locking solenoid was on the right of
the keylock.

Arnold

 

Try a little K-Y on the backdoor lock ;-)

 

Hi Viktor, when you take this thing apart you will see that the "cam" that
rotates when you move the key, also has a rod connected to it, the rod is
operated by the lock/unlock solenoid (or motor), so that you operate the
locking mechanism either by the central locking or by the key. In any
event, if I recall correctly, there was a piston that goes through a hole,
and the whole thing was rusted shut, after some wire brush and grease, the
whole thing was as good as new. The locking solenoid was on the right of
the keylock.

Arnold

 

Those lock cylinders on the 700/900 are very corrosion prone. Chances
are the only cure will be replacement, or you could just ignore it and
trust the power lock not to fail. Even if it does fail, you can still
open the tailgate from the inside, provided the child-proof lock is not
engaged.

 

What is K-Y ? Living in central Europe I don´t know what it is. We have
sprays containing MoS2 for lubrication of rusted or corroded mechanical
stuff. Is it something like that?

BTW it does not feel like rusted mechanics, it really feels like friction
between the plastic parts of the cylinder which I interprete as possible
consequence of oil dripping on it by accident.

Viktor Weisshäupl

 

K-Y Jelley is a lubricant in medical use (including sexual use). Much better to
use either WD40 or Duck Oil.

Cheers, Peter.

:
: : > Try a little K-Y on the backdoor lock ;-)
:
: What is K-Y ? Living in central Europe I don´t know what it is. We have
: sprays containing MoS2 for lubrication of rusted or corroded mechanical
: stuff. Is it something like that?
:
: BTW it does not feel like rusted mechanics, it really feels like friction
: between the plastic parts of the cylinder which I interprete as possible
: consequence of oil dripping on it by accident.
:
: Viktor Weisshäupl
:
:
:
:

 

Which raises the next question - what is WD40? Any hints on the chemistry of
that stuff?

Viktor

 

It is a special lubricant, waterproofer, contact cleaner, etc. that has been in
use in the UK for many years. It was developed for the Armed Forces as a
multi-purpose liquid not long after WW2. I used it when I was in the RAF
servicing V-bombers.

Cheers, Peter.

:
: : > K-Y Jelley is a lubricant in medical use (including sexual use). Much
: better to
: > use either WD40 or Duck Oil.
:
: Which raises the next question - what is WD40? Any hints on the chemistry of
: that stuff?
:
: Viktor
:
:

 

Most reports indicate it based upon kerosene (which you may know as
paraffin, a liquid used as lamp and stove fuel). The real formula is
a trade secret.

More indepth guessing can be found at:

http://www.newton.dep.anl.gov/askasci/chem00/chem00165.htm


Gary

 

[ ... ]

It first appeared on store shelves in 1958, five years after it was
invented in 1953--a good bit after WW2. When were you in the RAF?

WD-40 history:

http://www/wd-40.com/AboutUs/our_history.html


Gary